Ashes to Ashes - Dust to Recycling

Green transition 7 July 2017 Bettina Kamuk

The small Danish company Afatek has a world record in recovering valuable metals and minerals from ashes. Ramboll helped make the process even more efficient.

8 min

Director Jens Kallesøe from Afatek grabs a ballpoint pen and starts to dismantle it.

“This ordinary ballpoint pen contains four different materials: On the outside is a belly belt and a clip, both made of stainless steel. Two pieces of plastic tubing hold it all together. Inside is an ink tube made of plastic. One end has a stainless steel spring, and the other a small brass piece, where the ink comes out. So we found two types of plastic and two types of metal with sizes down to 1 mm,” he says, now with four different pen pieces in his hands.

“Basically, you now have two ways of putting this into a circular economy: You can let people do the job of dismantling the ballpoint pen by hand. Or you can take the pen to a waste-to-energy plant for recovery. There, the plastic is incinerated and recovered as heat and electricity. This frees the metals, which can now easily be separated and recovered in our new metal sorting plant. This is both economically and environmentally efficient because we can do it on a large scale. That’s what we do here.”

Outside Jens Kallesøe’s small office on Copenhagen’s island of Amager lie mounds of ash from waste-to-energy (WtE) plants. In other countries much of this material ends up in landfills. But here at Afatek ashes are not just ashes. Jens Kallesøe and his employees recover valuable metals and mineral resources from this dust.

Few do this better than the small Danish company. The technology at the new plant can identify and reuse metals down to 0.5 mm, thus creating a new industry standard much better than yesterday’s 4 mm.

Lower consumption of natural resources

Afatek is owned by five public waste companies and covers one third of the Danish market. The trucks that pass through the company’s gate unload around 200,000 tonnes of bottom ash a year. In the company’s new plant, which Ramboll assisted in constructing, the ash typically dries for two months before being put on the conveyer belts.

The new separation technology was developed with support from the Danish Environmental Protection Agency. The technology features magnets for ferrous recovery, fast-moving magnets for non-ferrous recovery and sensor machines for recovering stainless steel.

“The fine-line conveyer belt is where you find the technology that can recover the piece of brass from the ballpoint pen – which is just over 0.5 mm thick,” says Jens Kallesøe.

The new technology increases the recovery rate for brass, aluminium, copper, zinc and stainless steel by 50%. It also lowers the consumption of natural resources – thereby saving CO2.

In total Afatek comes close to recovering 90% of the metals in bottom ash. The residue – a kind of gravel – is a valuable resource in road construction. In Denmark a total of 600,000 tonnes are recovered each year, thus reducing human interference with the ecosystems present in and around traditional gravel pits.

Recovers heating and electricity

The key to creating this part of a circular economy is to combine the thermal sorting done at WtE plants with the mechanical magnetic sorting done at plants like Afatek.

“The thermal process reduces complexity and recovers energy – in terms of not only heating but also electricity. And the mechanical sorting further reduces complexity – which results in sales-quality metals and minerals for use as gravel for road construction,” explains Jens Kallesøe.

After a few years’ scepticism from other circular economy industries, companies like Afatek are now considered both economically and environmentally viable. And the export potential is about to be realised.

The biggest order so far has been placed by another metropolitan island – Singapore – where Afatek has worked with Ramboll to supply know-how to the biggest WtE facility in the world.

Written by Michael Rothenborg.